The invention relates to reinforcing components for elastomeric products, and elastomeric products made using the reinforcing component. In an illustrated embodiment, the reinforcing component is a belt package for a pneumatic tire.
Elastomeric products, such as drive belts, conveyor belts and pneumatic tires are sometimes made with reinforced components, wherein the reinforcement is parallel cords or filaments encapsulated in a rubber matrix. Often, more than one of these components need to be layed up in the product adjacent to another such component, and most often, when more than one layer of reinforcement is used, the cords or filaments in adjacent components have opposing angles. Such components have edges with exposed reinforcement ends, and splices, especially in belts and tires.
When an elastomeric product works, there is a tendency, over time, for the ends of the reinforcement, and the edges of components that have physical properties different from the elastomer, to break free of the elastomer. Also, splices can break loose from the elastomer and cause separations of the reinforcing component from the elastomer. Often, additional components are added to the product, or the product is otherwise modified, to reduce or eliminate these problems.
With respect to radial pneumatic tires, European Patent Application (EPA) 0875402A attempts to solve this problem by providing two belt layers comprising an inclining strip, formed by aligning a plurality of reinforcing cords to a tire circumferential direction, and extending it zig-zag in the tire circumferential direction so that the strip is turned back from the lower belt layer to the upper belt layer at both end portions of the two belt layers. A tire made using this type of reinforcement is said to improve straight driving stability while improving edge separation resistance of the belt layers.
Although the zigzag folding of an elastomeric reinforced strip eliminates the problem of cord ends at a belt edge, such strips still contain a splice. Because two layers of belt are created from a single strip of reinforced elastomer, and the upper belt layer and lower belt layer are disposed at opposed angles, the conventional overlap splice and the conventional butt splice cannot be used with this configuration. The challenges of this kind of construction is to create a splice that can be made with a minimum amount of cutting, i.e., a splice that is not labor intensive, and to create a splice that provides a smooth transition in the composite, i.e., in a completed tire, there are no bulges caused by stacking material in an overlap splice.
It is an object of this invention to provide a reinforcing component which can be used in elastomeric products that does not have cut edges comprising free ends of cord or filament reinforcement, and appears to be substantially spliceless in a completed product.
Other objects of the invention will be apparent from the following description and claims.
xe2x80x9cApexxe2x80x9d refers to a wedge of rubber placed between the carcass and the carcass turnup in the bead area of the tire, usually used to stiffen the lower sidewall of the tire.
xe2x80x9cAxialxe2x80x9d and xe2x80x9caxiallyxe2x80x9d means lines or directions that are parallel to the axis of rotation of the tire.
xe2x80x9cBeadxe2x80x9d means that part of the tire comprising an annular tensile member wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim.
xe2x80x9cBelt reinforcing structurexe2x80x9d means at least two layers of plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 17 degrees to 28 degrees with respect to the equatorial plane of the tire.
xe2x80x9cCarcass plyxe2x80x9d means the tire structure apart from the belt structure, tread, undertread, sidewall rubber and the beads.
xe2x80x9cCordxe2x80x9d means one of the reinforcement strands of which the plies in the tire are comprised.
xe2x80x9cEquatorial plane (EP)xe2x80x9d means the plane perpendicular to the tire""s axis of rotation and passing through the center of its tread.
xe2x80x9cFilamentxe2x80x9d refers to a single yarn.
xe2x80x9cPantographingxe2x80x9d refers to the shifting of the angles of cord reinforcement in a tire when the diameter of the tire changes, e.g. during the expansion of the tire in the mold.
xe2x80x9cPlyxe2x80x9d means a continuous layer of rubber-coated parallel cords.
xe2x80x9cPneumatic tirexe2x80x9d means a mechanical device of generally toroidal shape (usually an open torus) having beads and a tread and made of rubber, chemicals, fabric and steel or other materials. When mounted on the wheel of a motor vehicle, the tire through its tread provides a traction and contains the fluid or gaseous matter, usually air, which sustains the vehicle load.
xe2x80x9cRadialxe2x80x9d and xe2x80x9cradiallyxe2x80x9d means directions radially toward or away from the axis of rotation of the tire.
xe2x80x9cRadial-ply tirexe2x80x9d means a belted or circumferentially restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65 to 90 degrees with respect to the equatorial plane of the tire.
xe2x80x9cShoulderxe2x80x9d means the upper portion of a sidewall just below the tread edge.
xe2x80x9cSidewallxe2x80x9d means that portion of a tire between the tread and the bead.
xe2x80x9cSplicexe2x80x9d refers to the connection of end of two components, or the two ends of the same component in a tire. xe2x80x9cSplicexe2x80x9d may refer to the abutment or the overlapping of two such ends.
xe2x80x9cTreadxe2x80x9d means a molded rubber component which, when bonded to a tire casing, includes that portion of the tire which comes into contact with the road when the tire is normally inflated and under normal load.
The invention relates to a pneumatic tire having at least a pair of substantially parallel annular beads (12), at least one carcass ply (14) wrapped around the beads, a tread (18) disposed over the at least one carcass ply in a crown area of the tire, and sidewalls (20) disposed between the tread (18) and the beads (12). A reinforcement package (24) is disposed between the tread (18) and the at least one carcass ply (14) in the crown area of the tire, the reinforcement package (24) comprising an elastomeric composite having a second end 44 and a first end (32). The elastomeric composite is reinforced with substantially parallel reinforcement cords (26) oriented at substantially 0xc2x0 with respect to a longitudinal centerline (CL) of the composite, and the composite is folded upon itself to provide reinforcement package (24) having an upper layer (46), characterized in that reinforcement cords therein have an angle of 17 to 35xc2x0 with respect to the equatorial plane (EP) tire (10), and a lower layer (48), wherein reinforcement cords therein have an angle of xe2x88x9217 to xe2x88x9235xc2x0 with respect to the equatorial plane (EP) of tire (10). The reinforcement package (24) has a splice (28) wherein upper layer (46) at second end tip (37) overlaps with lower layer (48) at a first end (32). The splice (28) comprises a triangular configuration made by cutting upper layer (46) at first end (32) at angle of 17 to 35xc2x0 with respect to the width of the composite strip for a distance corresponding to 70 to 90% of the width of elastomeric composite (24), and removing all cut reinforcement cords (26) from cut-out (30) at first end (32).
Second end 44 of reinforcement package (24) fits with and overlaps with cut end (32) of reinforcement package (24) without modification.
The reinforcement cords (26) may comprise steel, polyester, polyamide, aromatic polyamide, reconstituted cellulose, polyvinyl alcohol, fiberglass, carbon-fibers and mixtures thereof.
In the illustrated embodiment, the reinforcement cords (26) are selected from the group comprising polyethylene naphthalate, terephthalate, rayon and aramid. The reinforcement cords (26) have a dTex of 3300 to 13000 and an end count in the reinforcement package (24) of 4 to 11 ends per centimeter (e.p.c.).